There is provided a process for increasing the Cetane Index of a distillate fraction by reacting the fraction with hydrogen over a catalyst comprising a hydrogenation component and zeolite beta.
Legislation mandating lower aromatics and increased Cetane Index (and number) of the distillate pool will have a major impact on refinery operations. Reduction of aromatics, especially particulate forming polynuclear aromatics, can be achieved by hydrocracking, hydrogenation, ring opening (decyclization), or a combination of ring opening and hydrogenation. A process utilizing a zeolite-based catalyst in conjunction with Pt for the reduction of benzene by utilizing hydrogenation and acid functionalities to hydrogenate/decyclize the benzene has previously been disclosed in Published International Application (PCT) Publication No. WO 93/08145.
In accordance with the present invention, the concept of reducing benzene is extended to the reduction of polynuclear aromatics in process streams containing high levels of polynuclear aromatics, e.g., light cycle oils, and vacuum distillates. In doing so, Cetane Index and number can be improved significantly without significant H.sub.2 consumption and distillate yield loss.
Although the hydrodecyclization of mono-ring aromatics has been demonstrated previously in the above-mentioned PCT WO 93/08145, the extension of this approach to multi-ring, distillate range feeds is not trivial. Boiling point conversion (distillate yield) and H.sub.2 consumption must be weighed against improvements in product properties.
Publications such as EP 512652 (May 5, 1992); EP 303332 (Aug. 11, 1988); EP 247678 (May 15, 1987); U.S. Pat. No. 5,147,526; and U.S. Pat. No. 4,921,595 suggest that USY-based catalyst systems containing Pt and/or Pd are active catalysts for upgrading Cetane Index through the conversion of distillate streams.